1. Field of The Invention
This invention is directed to a 2-D (X-Y axis) translation stage, which has a long travel range and high resolution. Moreover, a CD pick-up head, which is a low cost optical probe, is integrated with a Z-axis piezoelectric stage and an analog linear controller to be an optical autofocus system.
2. The Prior Art
Along with unremittingly progress of the precision engineering, in spite of the semiconductor industry, precision machinery industry, biological cell realm, optoelectronic system, microscopic organism, surface engineering, STM, SPM etc all make headway for microminaturization and precision. The needs of a micro or sub-micro position system are growing in number day by day, now there are already many precision position instruments in the industry field.
High-resolution position apparatus, constituting the drive of wafer stepper, is the most important item. However, there are already many precision position instruments or equipment in the industry at the present time. The instruments are limited by their resolution, therefore the total displacement is usually very small, and maximum travel range roughly reach only 200-300 xcexcm. An example of manufactures of the wafer in semiconductor industry, apparent from the diameter of eight of inches wafer roughly is 200 mm, however processing technology of 12 inches of wafer, even more than a larger size wafer, have already become the main point. With these instruments, precision is enough, but characteristic of a position for total travel range is insufficient. This incapability will not satisfy the needs of future the semiconductor and precision engineering industries.
For development of the optical lithography using 193 nm Excimer Laser, a single degree of freedom (Z-axis) and a high precision piezoelectric stage, with a double degree of freedom (X-Y axis) stepper must be designed and fabricated. The single degree of freedom driver is used for focusing the application of the Excimer Laser, and the main function of an optical autofocus system is to make the operating plane of the Z-axis piezoelectric stage, which is always maintained, in the focus-operating scope of the Excimer Laser. A double degree of freedom stepper is used as an application of the etching wafer by the methods of Step- Repeat- Projection and Step- Scan- Projection.
Making use of the optical-focusing system is very extensive, all without exception a CD-ROM, DVD, optical measurement probe, surface measurement instrument etc., are all important application of them. U.S. Pat. No. 5,008,705 disclosed an autofocus system which is applied to microlithography, assembly of lens, beamsplitter, and reflector. The system is used to automatically focus on a wafer, but its optical principle is not for the astigmatic method. U.S. Pat. No. 5,783,340 discloses a semiconductor wafer etching technique, which has equal depth fillister in the wafer that is used as the reference plane of the automatic focusing, detect movement, position and tilts of the wafer surface. ROC Patent No. 334888 describes an ultra high resolution 3-D micropositioner, which makes use of a piezoelectric-driven stage, that combined with mechanism of flexible contact, attempts to achieve the need of three-axes precise position, because using principle of flexible deformation, the position system can""t achieve the long travel range. The 3-D non-contact measurement instrument includes the XY slide and the extend arm, which is connected with a projector and has an electromagnetic-driven motor. The motor is controlled by a computer slew to the appropriate angle. A problem is that the capability of the position resolution of the motor is worse than the piezoelectric material, which can generate cumulating error at over-slewing angle.
Methods of using a stepper in the market make use of the DC motor, stepping motor and ball bearing of leading screw type that they put in use of the electromagnetic principle. The creator of the wafer stepper can satisfy the semiconductor various needs of the industry, and with meticulous care, to research and create a modem wafer stepper after which is used in the application of the deep ultraviolet lithography etching wafer.
An object of the invention is to provide a novel wafer stepper which can cooperate with the needs of 193 nm DUV Lithography.
Another object of this invention is to provide the piezoelectric stage, which is single degree of freedom(Z-axis) and high translation resolution.
A further object of the invention is to use a CD pick-up head that is a low cost optical probe integrated with Z-axis piezoelectric stage and analog linear controller, to be an optical autofocus system.
An object of the invention is to provide a 2-D(X-Y) translation stage, which is in the long travel range and with high resolution.
These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.